Cimetidine does not demasculinize male rat offspring exposed in utero

Cimetidine has weak antiandrogenic activity in rats, but does not affect fertility in male rats at daily doses up to 950 mg/kg. Literature reports have claimed that giving cimetidine to pregnant rats in the drinking water caused feminization of male pups, small sex organs, low libido, and low serum testosterone. In the present study these effects were tested by giving large groups of pregnant rats 180 mg/kg/day cimetidine in the drinking water from Day 12 of pregnancy until the end of lactation, or a combination of drinking water and gavage treatment. Estimations included anogenital distance exactly 24 and 120 h after birth; serum testosterone at 55 and 110 days of age; mating performance at 110 days and (after castration and testosterone implantation) at 143 days; and testis, prostate, and seminal vesicle weights at 55 and 147-148 days. Maternally administered cimetidine was completely without effect on all the parameters measured in the male offspring. Thus, giving cimetidine to pregnant rats did not affect the masculinity of their male offspring.